Here \(\Delta g\)  is the difference of the g factors of the two non-equivalent
sites; it is a maximum at 45\(^\circ \)  between \(b_m\)  and \(c_m\) . This condition,
mathematically proven by P.W. Anderson [1]}, was used to
directly estimate the interchain coupling in the quantum spin chain CuGeO\(_3\) 
[2]}. The intrachain exchange interaction of (TMTTF)\(_2\) X
(\(\sim \) 400 K) is too large and all the chains in the configuration \((\pi ,\pi )\) 
in Fig.REF  should have the same resonance field (only one line
is expected). In the configuration \((0,\pi )\) , two kinds of chains exist : full
A and full B. Compared to Ref.[3]}, the configuration
\((\pi ,\pi )\)  is the scenario (c), \((\pi ,0)\)  is the scenario (d), \((0,0)\)  is the
scenario (a) (and is the standard picture to explain the CO transition),
\((0,\pi )\)  is not mentioned. Since we can resolve two lines, we are able to
decouple the signals from two different chains. Thus we are able to give an
upper limit for the smallest interchain coupling \(J_c\) .
<TABLE><FIGURE>